Equisetum arvense (scouring rush; field horsetail; western horsetail)

Wikipedia Abstract

Equisetum arvense, the field horsetail or common horsetail is a herbaceous perennial plant, native throughout the arctic and temperate regions of the northern hemisphere. It has separate sterile non-reproductive and fertile spore-bearing stems, growing from a perennial underground rhizomatous stem system. The fertile stems are produced in early spring and are non-photosynthetic, while the green sterile stems start to grow after the fertile stems have wilted, and persist through the summer until the first autumn frosts. It is commonly confused with mare's tail, Hippuris vulgaris.

Large quantities of the plant can be toxic. This is because it contains the enzyme thiaminase; In small quantities this enzyme will do no harm to people eating an adequate diet that is rich in vitamin B, though large quantities can cause severe health problems. The enzyme is destroyed by heat or thorough drying, so cooking the plant will remove the thiaminase;
The plant also contains equisetic acid - see the notes on medicinal uses for more information;

The stems contain 10% silica and are used for scouring metal; They can also be used as a polish for brass, hardwood etc;
The infused stem is an effective fungicide against mildew, mint rust and blackspot on roses; It also makes a good liquid feed;
A light pink dye is obtained from the stem; It is yellow-gray according to another report;
The plant has been used for making whistles;